Recently, an inkjet recording apparatus which includes a plurality of motors has been popular to meet various types of operations such as scanning of a printhead, feeding of recording paper, conveyance of recording paper under a recording state, and maintenance of a printhead.
A motor driver used in an electronic apparatus like an inkjet recording apparatus, which is structured as one IC by including a multi-axis driving circuit capable of driving a plurality of motors, has been increasing in number.
The DC/DC converter circuit has been conventionally included an overcurrent detection means, overvoltage detection means and an internal temperature detection means as a detection means for detecting failure and malfunction. The overcurrent detection means detects that the current running through a MOS transistor of a DC/DC converter has exceeded a prescribed value (refer to Japanese Patent Laid-Open No. 9-037347).
The reason an overcurrent occurs is roughly divided into two cases: one is occurrence of failure such as short-circuit; the other is load current of the DC/DC converter in an overloaded state.
The overvoltage detection means detects that an output voltage of the DC/DC converter has changed by approx. 30% up and down.
The overcurrent detection means of the DC/DC converter is configured so that the overcurrent generated when a power supply (VBUS) is applied to an apparatus connected through a USB interface may be detected.
As mentioned above, the motor driver includes the multi-axis driving circuit capable of driving a plurality of motors and is configured as one IC. To configure one IC (integrated circuit), a regulator, DC/DC converter, reset circuit or the like may be further assembled.
When the above-mentioned overcurrent detection means (or overvoltage detection means) is detected, the output stage of the DC/DC converter is OFF-controlled by taking it as failure occurring in an IC (integrated circuit) including the overcurrent detection means, and the motor driving circuit is controlled so as to stop.
In the case that the reset function is included, a reset signal for setting the IC of which power supply is fed from the DC/DC converter of the motor driver to a reset condition is asserted.
With the above-mentioned configuration, overcurrent protection by overcurrent detection of the DC/DC converter, overvoltage protection by overvoltage detection, and overheat protection of IC by an IC internal temperature detection means operate and, if any DC/DC converter or motor driving circuit falls into a stopping condition, the DC/DC converter or the motor driving circuit is not recovered any more until a power supply inputted in the motor driver is turned off once, and a power switch is turned on again after power voltage drops below a prescribed voltage level.
Where the DC/DC converter built in the motor driver supplies power to CPU, power supply to the CPU is turned off once the power supply of the motor driver is turned off.
That is, if any of the protection circuits operates, the power supply of the CPU is turned off, so that the CPU cannot recognize which of the protection circuits operates.